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A Better Way to Measure Catfish Feed Intake, GrowthBy Tara Weaver-MissickAugust 4, 1999 Tiny glass beads mixed with catfish feed are helping Agricultural Research Service scientists track how food intake affects catfish growth. Research geneticist Jeffrey T. Silverstein, based at the ARS Catfish Genetics Research Unit in Stoneville, Miss., developed this technique. Until now, it’s been difficult to measure how much food an individual fish eats daily, because all fish are raised together in a pond and fed simultaneously. It’s easier to measure feed intake with land animals, because feed can be weighed before and after, and then calculated to determine what each animal consumed, according to Silverstein. Generally, catfish producers record feed intake based on simple observation, but this method assumes that fish consumed all the feed delivered and that they all ate the same amount. Silverstein adapted an innovative technique from salmon feeding studies--tiny glass beads in the feed--and customized it for channel catfish. The opaque glass beads are about 0.4 millimeters in diameter. They are mixed into the feed in low concentrations of about 1 percent of the feed. After feeding, catfish are anesthetized and x-rayed. This allows the beads to be counted so that an accurate feed calculation consumed by each fish can be taken. Fish with superior feed intake and conversion of feed into filet meat can be identified, so this trait can be incorporated into breeding programs. Silverstein has perfected the technique even more by automating the bead counting process. This allows him to view 600 scanned x-ray images a day, versus 200 images over a few weeks when done by hand. Automation is nearly 100 percent accurate. In indoor tank studies ARS scientists found different catfish strains consume feed at different rates. This information will help them to make genetic improvements in channel catfish. An article on the research also appears in the August issue of Agricultural Research magazine. The story is also on the World Wide Web at: /is/AR/archive/aug99/feed0899.htm Scientific contact: Jeffrey T. Silverstein, ARS Catfish Genetics Research Unit, Stoneville, Miss., phone (601) 686-3591, fax (601) 686-3567. |
